2022-2023 Science Planning Summary
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2022-2023 USAP Field Season
Project Detail

Project Title

AESOP-lite: Anti-Electron Sub-Orbital Payload – Low Energy

Long Duration Balloon Facility. Photo by Peter Rejcek. Image courtesy of NSF/USAP Photo Library.
A-148-M Research Location(s): McMurdo LDB Site


Event Number:
NSF / NASA Agreement

Program Director:
Dr. Vladimir Papitashvili

ASC POC/Implementer:
John Rand / Kaija Webster / Chad Naughton

Principal Investigator(s)

Dr. John M Clem
University of Delaware
Physics and Astronomy

Project Web Site:


Supporting Stations: McMurdo Station
Research Locations: McMurdo LDB Site


The primary science objective of this project is to make a definitive determination of the cosmic electron and positron energy spectrum from 20MeV to above 500MeV. Toward this objective, the goal of this effort is to explore the source of the negative spectral index of low energy cosmic ray electrons (20-100MeV) by attacking the problem on two fronts. First, electrons in the energy range of 20MeV to 300MeV will be measured with the AESOP-lite instrument on a high-altitude balloon floating at >140kft. This data will provide a clean, calibrated reference at 1AU to be compared with Voyager electron observations from interstellar space. Voyagers I and II are currently returning electron spectra roughly within this energy range (<160MeV). Second, measurements of the positron fraction in the electron flux within this low energy regime will be taken simultaneously using the same instrument. Positron abundances in this energy range should be highly diagnostic of the particle origin. The desired mission profile is a minimum exposure of 40hrs above 140kft from a high magnetic latitude region. This will provide a clean measurement of electron spectra from 20MeV to 100MeV.

Field Season Overview

Six participants will deploy in the 2022-23 season. In preparation of the balloon flight, the AESOP-lite payload will be assembled, evaluated for functionality and calibrated. This includes the integration of CSBF's flight equipment with the payload and a final compatibility test while hanging from the launch vehicle. A 400ft^2 assembly area with an 1/2 ton overhead lift is needed to perform these operations including 5 x 120V 60Hz power outlets with a peak current 10amps for each outlet. Also internet service is necessary to communicate with Operation Control Center at CSBF. We request three static IPs. One of the detectors in the instrument, a Gas Cherenkov detector, uses C3F8 gas and may require refilling before flight. Consequently 10lbs of C3F8 is required in the field. In order to re-validate the flight O-ring and feed-thru gasket integrity, on the ground, the instrument flight shell is pressurize with Nitrogen gas to 14.7 psi over ambient over 48 hours. This procedure simulates the pressure differential expected at float. This test takes place in an empty Sea-container. Therefore, T-size bottom of Nitrogen is needed. AESOP-lite's goal is to be ready to launch early-December on a 60 million cubic foot balloon platform. Desired float altitude is 155k-feet. Duration goal is 80 hours at desired height or one full circumpolar rotation.

Deploying Team Members

  • John Clem (PI)
  • Paul Evenson (Co-PI)
  • Robert Johnson (Co-PI)
  • Brian Lucas
  • Pierre-Simon Mangeard
  • James Roth